Convertible desk



FIG. 1 is a left front perspective view showing the convertible desk of my new design;

FIG. 2 is an upper left side perspective view thereof;

FIG. 3 is a rear plan view thereof;

FIG. 4 is a left side view thereof;

FIG. 5 is a front view thereof;

FIG. 6 is a right side view thereof;

FIG. 7 is a top view thereof; and,

FIG. 8 is a bottom view thereof. 

The ornamental design for convertible desk, as shown. 